Various wireless communication technologies are being developed in accordance with advancement of information communication technologies. Wireless communication technologies may be generally classified into technologies using licensed bands and technologies using unlicensed bands (e.g., industrial-scientific-medical (ISM) band) according to bands used by respective technologies. Since a licensed band is exclusively used by a specific operator, the technology using the licensed band may provide better reliability, communication quality, etc. than that using an unlicensed band.
There exists, as a representative cellular communication technology using a licensed band, a Long Term Evolution (LTE) or LTE-Advanced (LTE-A) standardized in a 3rd generation partnership project (3GPP). Thus, a base station or a user equipment (UE) supporting LTE or LTE-A may transmit or receive signals through a licensed band. Also, there exists, as a representative wireless communication technology using an unlicensed band, a wireless local area network (WLAN) defined in IEEE 802.11. Thus, an access point or a station supporting the WLAN may transmit or receive signals through the unlicensed band.
Meanwhile, as mobile traffics are increasing explosively, additional licensed bands are required in order to process such the increasing mobile traffics through licensed bands. However, licensed bands are limited resources. Since a licensed band is obtained usually through an auction held among operators, astronomical investment may be demanded for obtaining an additional licensed band. In order to resolve the above-described problem, a method for providing LTE or LTE-A services through an unlicensed band may be considered.
In the case that the LTE (or LTE-A) services are provided through the unlicensed band, coexistence with the communication nodes (e.g., access points, stations, etc.) supporting the WLAN is needed. For the coexistence in the unlicensed band, a communication node (e.g., base station, UE, etc.) supporting the LTE (or LTE-A) may occupy the unlicensed band based on an LBT (listen before talk) scheme. For example, a communication node supporting the LTE (or LTE-A) may determine a contention window by performing a random backoff operation, randomly select a backoff value within the determined contention window, and occupy the unlicensed band when a status of the unlicensed band is idle for a time corresponding to the selected backoff value.
Here, the size of the contention window may be changed statically or dynamically. However, a procedure for changing the size of the contention window in the unlicensed band where the LTE (or LTE-A) services are provided is not clearly defined. Further, there is a problem that the size of the contention window is changed without considering the status of the unlicensed band.
Meanwhile, this description on the related arts is written for understanding of the background of the present disclosure. Thus, information on other than conventional technologies, which are already known to those skilled in this technology domain to which the technologies of the present disclosure belong, may be included in this description.